Dns not updating from dhcp
If there is no timestamp, such as a manually created, static record, it will not get scavenged.
Also, if all servers, including DCs, are automatically updating their own record, then there is no fear of losing their records, because for one, their records (timestamps) are current, therefore scavenging won’t touch them, and two, Windows Servers by default will update their records every 24 hours, with the exception of domain controllers at every 60 minutes.
For domain controllers, due to the importance of keeping up to date and accurate SRV and other records, the Netlogon service will attempt to update these records every 60 minutes.
This is because DHCP doesn’t own the record, the client does, even though DHCP registered it.
The way to get around this is you can configure DHCP’s Option 081 to update the record for all client, no matter if the client asks or not.
This is because the client will not update itself due to the current record in DNS is beyond the lease period.
This happens even though DHCP registered the record.